Objectives

Microsphere Preparation

Due to the relatively unsuccessful preparation of PVA/clay microspheres(the prepared spheres were either larger than a micrometer or did not appear at all), a new method was used for the preparation of PVA/clay microspheres.

General Protocol:

The desired ratio of PVA and clay was measured out. The total mass was ~1g.

The PVA/clay was placed in a 50mL beaker with a magnetic stir bar. 25mL distilled H2O were added to the beaker and the solution was heated to ~100°C and allowed to stir until complete dissolution of PVA/clay.

The magnetic stir bar was removed and 25mL of mineral oil was added to the beaker.

The contents of the beaker were poured into a blender to homogenize the solution and create an emulsion of the aqueous and organic layer in the attempt to create a suspension of microspheres.

The blender was turned on a low setting for 5 minutes.

The contents of the blender were poured into a beaker and the appropriate amount of DMSO/Rhodamine 6G solution was added.

The microsphere solution was placed in a freezer at -20°C for 24 hours and then removed and allowed to thaw for 24 hours.

After the addition of dye/DMSO to the 110% Lamponite, the dye appeared to stick to very small spheres at the bottom of the beaker. Bright pink spheres immediately formed. This did not occur for the samples containing 110% NaMT.

Fluorescence

The six hydrogel samples that were allowed to soak in Rhodamine 6G were tested for the rate of diffusion of Rhodamine 6G from the samples.

General Protocol:

Excess Rhodamine 6G sample still present in the beaker was removed.

Hydrogel samples were removed from the beakers, pat dry with a paper towel, and placed in a new, clean beaker.

25mL distilled H2O were added to each beaker sample.

A timer was started, and every 15 minutes, a sample of distilled H2O was removed from the beaker and placed in an unfrosted cuvette.

The sample was discarded into a waste beaker.

This process was repeated for 2 hours.

Spectra:
Observations:

Each of the samples had a very fast diffusion rate. If the spectra are viewed additively for each hydrogel sample, a significant amount of dye leaked out of the hydrogel sample in only 2 hours, in comparison to the hydrogels which remained in distilled H2O for one week and had minimal dye diffusion. This indicates that the dye must be added prior to the freeze-thaw crosslinking method.

Due to the fact that the dye did not immediately, completely diffuse out, the crosslinking of PVA/clay hydrogels slowed the diffusion rate of the dye.

Comparing the 50:50 ratio of PVA:clay and the 90:10 ratio, the hydrogels with 50:50 ratio had more dye leak out of the hydrogel than the 90:10 ratio. Perhaps indicates a more effective pressure stimuli.

In the future, when performing the diffusion tests, after taking a sample every fifteen minutes, the sample will be readded to the test beaker rather than discarded.